Lens



May 23, 1933. E T1| YER 1,910,483

LENS

Filed May l5, 1928 'i La at about the distance of the feet from the eye field of which incorporates a third field ads Patented May 23, 1933 UNITE vsrares ATENT ol-*riceA i EDGAR-D. TILLYER, OF SOUTHBR-IDGE, T.vASSiACESETTS, .ASSIGNOR T AMERIOAN- OPTICAL CORPORATION, OF SOUTHBRIDGE, MASSACHUSETTS, .A VOLUNTARY .ASSO- CIATION OF MASSACHUSETTS L LENS Application filed May 15, 1928. Serial No. 278,013.

the eye.- The displacement or jump Iin a multifocal lens in going from one field to the other field is in proportion to the sizeof the reading field, the smaller the field, the smaller the displacement or jump encountered. One of the difficulties of multifocal lenses vhas always been the adjustment of the Vpatients vision in the use of bifocals or multifoc'al lenses when the lpatient is walking and par# ticuiarly when he is going over obstacles such as the curbs of pavements and the steps of stairways. This trouble has been caused by the fact that the reading field is of short focus and objects seen from a distance ofthe eyes to the feet are blurred and this defect has caused serious accidents in many instances.` l i It is, therefore, one of the principal objects of myinvention to provide an economical process of making a lens having the characteristics of a small reading field incorporating means by which the distance to the feet from the eyes may be clearly and easily seen and to produce a new and useful prod-` uct by means of this process. Y

Referring to the drawing: F ig. ll isa front or plan view of a 'multifocal lens 'blank embodying the invention; Fig. 2 isa cross section on line 2 2 of Fig. l showing a multifocal lens `the multifocal curves of which are on the convex sur'- face of the blank; i

Fig. 3 is a cross section on line 2-2 of Fig. l showing the multifocal surfaces of which are on the concave side thereof; Fig.v 4 is a cross section on line 2-2 of Fig. l showing a plano vor flat blank having the multifocal curves onl one lside thereof;

Fig. 5 is a front or plan view of a multifocal lens incorporating the invention and showing a dierent arrangement of the fields; 1

This invention relates te improvements in multifocal lenses and has particular reference to an improved multifocal lens of one piece of glass.

5 The principal object of the invention is to provide an improved multifocal lens which will provide a reading field of a limited d1- mension and a third fie-ld either equal to the distance held or different in power from the other two fields.

Another object of the invention is to pro` vide an improved multifocal lens, the. reading field of which incorporates another field of different focal length. Y

Another object of the invention is to provide an improved multifocal lens having a third field incorporated within the reading field, said third field being ofthe samepower as the distance held, whereby objects located may be clearly seen.

Another object of the invention is to provide an improved multifocal lens, the reading justed to some desirable focus other than that of the reading field.

Another object of the invention is to pro-V vide a more inexpensive method of producing multifocal lenses having a reading field in which is incorporated a third field of differentfocus therefrom. Y

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawing and it will be apparent that many changes may be made in the details of construction, arrangement of parts and steps of the process without departingfrom the spirit of the invention as expressed in the accompanying claims. I, therefore, do not wish to be limited to the exact details and arrangements shown and described as the vpreferred forms only have been shown by way of illustration.

In the development of multifocal lenses, particularly in the development of useful bifocal lenses, there is a growing tendency to diminish the size of the reading field and make that eld as small in dimension as is compatible Ywith good vision for the range of Fig. 5.

Referring to the drawing wherein similar reference characters denote corresponding parts throughout, I produce the mnltifocal lens shown in cross section in Fig. Q'as'follows: I mold a glass blank approximately to the meniscus or v which is to be produced with the multifocal Fig. 6 is a cross section on line 6 6 of i saucer shape ofthe lens Y fields thereon as shown in cross section in Fig. 2, and on one surface thereof I surface and finish the distance curvature 1 and the reading curvature 2. Thus far I have followed the well known procedure of making the so-called one-piece multifocal lenses Vin which the two curvatures 1 and 2 arev ground and finished on one side of a single piece of glass, the curvatures 1 and 2 merging with each other valong the line of their division 3. This `is accomplishedV preferably by the use of ring tool grinding, well known in the prior art. After having produced the curvatures l and 2 on the blank, I next surface off from the curvature 2 the curvature 4, which is preferably Yof the same radius as the curvature l. This then produces/the field 4 which is circular in shape and one portion of which is tangent at its lowest portion with the line of division 3 of the curvature 2. On the opposite side I then surface and polish the prescription curve 5 to produce the required power of the lens. It will thus be seen that the vision through the portion l of the lens will be distance vision; that the vision through the portion 2 will be the reading vision; and that vision through the portion 4 will also be the distance vision. rllhe curvature 4 is of the same vision as the distance portion for the reason that the curvature 4 is of the same radius as Vthe curvature l.

It is apparent that I do not need to locate the curvature 4 tangent with the division line 8 at the bottom thereof as shown in Fig. l, as I mayshift it anywhere along the ,center line from the point 6 to the point 7. It is also apparent that the vision through the portion 4 may be made the same as the distance vision through the portion l or may be'some other power, such as an intermediate distance, simply by regulating the radius of the curvature 4. n Y n In Fig. 3, I have shown amultifocal lens which is the same kind off lens as that of Fig. 2 having the distance curvature l, the reading curvature 2, and the distance curvature 4 again below the reading curvature 2, but the multifocal curvatures ,are placed on the concave side and the prescription curvature 5 is placed on the convex side thereof. These curves are produced in a manner similar to that of producing the curves of Fig. 2 and the sections 2 and 4 may be located in the various positions as referred to in connection with Fig. 2.

y Fig. 4 shows a pl ano type of lens in which the curvature 1 is a fiat surface or planoon which is located the reading curvature 2 and the plano field 4. The prescription side 5 is also plano. The field 4 may be located as in Figs. 2 and 3 and the lens is produced by a similar process. Y

In Fig. 6 I have showna multifocal lens in which the field 4 is located tangent at the point 7 instead of at the point 6, as in Fig. l. This lens is shown in cross section in Fig. 6, the bifocal curves being shown on the convex side of the blank, and is produced in a manner similar to the other forms.

AIt will be seen that I have produced a multifocal lens having la large comfortable distance field, a small reading field having small jump or displacementy when the vision 'passes from the distancel field Vthereto and have incorporated therewith a third field which may if desired be-made of the same power as the distance field for use in walking, or may be made in intermediate power or other foci as desired for various purposes, and that this field-4 may be located at desired positions between thev point 6k to ythe point/Z and the curvatures may be placed either on the convex or concave side, and that the lenses may be of the curved or meniscus form or of the fiat or plano form.

Having described my invention, I claim: l. A multifocal lens comprising on one side of a single piece of glass a major field having an optical surface thereover, a secondary field of greater power than the major field within the confines of the major field, said secondary field having an optical surface thereover, and being circular in outline and said field blending into the major field without difference in level along the line of division of the two fields and a third field within the confines of the secondary field, said third field having an optical. surface thereover of a curvature different 'from that of the major and secondary fields, said third field being depressedV into said secondary field and said field blending into the secondary fieldwithout difference in Vlevel along the line of division of the two fields. p U

2. A multifocal lens comprising on vone side of a single piece of glass a major field having an optical surface thereover, a secondary field within the confines of the major field, said secondary field having, an optical surface projecting outwardly beyond the surface ofthe major field, and said secondary field being circular in outline, said` field blending into the major field without difference in level along the line of division of the two fields and a third field within the confines of the secondary field, said third field having an optical surface thereover of a curvature different from .that of both the major and secondary fields.A said third field being circular in outline and being depressed into said secondary field and said field blending into the secondary field without difference in level along the line of division of the two fields. p

3. Al multifocal lens comprising on one side of a single piece of glass a major field having an optical surface thereover,a secondary field of greater power than the maj or field within the confines of the major eld1 said secondary ield having an optical surface projecting outwardly beyond the surface of the major field, and said secondary field being circular in outline, said field blending into the major eld without difference in level along the line of division of the two fields, a third field Within the confines of the secondary field, said third eld having an optical surface thereover of a curvature different from that of both the major and secondary ields, said third ield being circular in outline and depressed into said secondary field with its out-line tangent to the outline of the secondary field in the vertical meridian of the lens and said field blending into the secondary field without difference in level along the line of division of the two fields.

EDGAR D. TILLYER. 

